problems with local user format files

[Ulrike Fischer]

texlive creates sometimes (I don't know which events triggers this,
but it happened also for me more than once) local user format files
in .texlive2020/texmf-var/web2c

This format files are normally unwanted as they shadow the formats
from tlmgr update and I'm seeing an increasing amount of questions
triggered by such user formats, e.g.
https://github.com/latex3/latex3/issues/781, and of mysterious and
time consuming compilation failures on my own computer (at least the
first few times it happened it was quite time consuming to debug).   

I'm alone on my computer. I never run fmtutil-user manually and I
never want formats in .texlive2020/texmf-var/web2c. Is there a way
to avoid to get them? If some events triggers this format creation I
would greatly prefer to get an error about a faulty or missing
format. 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/